Hey OP, the split is very recent. Even if he doesn't love his wife any more, they were together for a LONG time.
I couldn't even have a 'fun' relationship for a year after splitting up with my wife, even though we tried everything to stay together. And after that, I was still, frankly, really sad. Not all the time, but it crept up on me when I least wanted it to.
And after that, I still thought about her a lot. It wasn't any more in a sexual or jealous way, but grieving the loss of the person who was once the love of my life, all the things we had planned and the break up of our family.
Your guy has baggage, as others have said. After a very long relationship, perhaps he's wondering what he really wants now. He's not even divorced, right? And the break up will stress him out massively. And yep, he will be worried about his daughter's feelings, too.
I think in this case, the more you reveal your insecurities, natural as they are, the more he will back off. Maybe say, oh, do you need time and space to sort this stuff out, and come back when you're ready? Something like that? Not saying end it, but if you push him, he might run away.